Heating device



FIG. 1 is a front plan view of the heating device;

FIG. 2 is a right side plan view of the heating device;

FIG. 3 is a left side plan view of the heating device;

FIG. 4 is a back plan view of the heating device;

FIG. 5 is a bottom plan view of the heating device; and,

FIG. 6 is a top plan view of the heating device. 

The ornamental design for a heating device, as shown and described. 